Tumbling apparatus for blending finely divided dry materials

ABSTRACT

A blender for intimately mixing and homogenizing relatively free-flowing finely divided powdered and granular materials. The blender is characterized by a vertically disposed circular chamber of relatively large diameter and relatively narrow width within a housing journaled for rotation about a horizontal axis. The chamber is fitted with a plurality of generally horizontal, widely spaced apart separation elements projecting from either or both of the side walls, spanning the width of the chamber and disposed in a substantially uniform array. As the housing is rotated, material to be blended is carried to the top of the chamber from where it falls onto the separation elements as it cascades downwardly. The material is divided successively as it passes over each separation element and then recombined as it falls through the chamber. Such division occurs hundreds or thousands of times in the course of the blending operation.

United States Patent Thoreson et al.

[ Sept. 17, 1974 TUMBLING APPARATUS FOR BLENDING FINELY DIVIDED DRY MATERIALS Inventors: Gene A. Thoreson, Santa Ana,

Califi; Richard A. Ley, Minneapolis, Minn.; Cardell E. Miller, Hudson, Wis; Lewis A. Emery, Minneapolis, Minn.

The Strong-Scott Mfg. Co., Minneapolis, Minn.

Filed: May 10, 1972 Appl. No.: 252,021

Assignee:

US. Cl. 259/3, 259/89 Int. Cl. B0lf 9/06, BOlf 15/02 Field of Search 259/3, 14, 30, 81 R, 81 A,

259/89, 90, 175, 176, 177 R, 177 A, DIG. 30

References Cited UNITED STATES PATENTS 3/1936 Chapman 259/D1G. 30 5/1942 Placek 259/3 UX 7/1950 Cornell 259/89 11/1950 Holcomb et a1. 259/30 1 H1965 Chadbourne et a1. 259/3 FOREIGN PATENTS OR APPLICATIONS l/l93l Great Britain 259/3 1,053,784 10/1953 France ..259/l4 Primary ExaminerHarvey C. l-lornsby Assistant Examiner-Philip R. Coe

[57] ABSTRACT A blender for intimately mixing and homogenizing relatively free-flowing finely divided powdered and granular materials. The blender is characterized by a vertically disposed circular chamber of relatively large diameter and relatively narrow width within a housing journaled for rotation about a horizontal axis. The chamber is fitted with a plurality of generally horizontal, widely spaced apart separation elements projecting from either or both of the side walls, spanning the width of the chamber and disposed in a substantially uniform array. As the housing is rotated, material to be blended is carried to the top of the chamber from where it falls onto the separation elements as it cascades downwardly. The material is divided successively as it passes over each separation element and then recombined as it falls through the chamber. Such division occurs hundreds or thousands of times in the course of the blending operation.

11 Claims, 8 Drawing Figures PAIENIED sin 1 m:

SHEET 3 OF 3 TUMBLING APPARATUS FOR BLENDING FINELY DIVIDED DRY MATERIALS This invention relates to apparatus for blending and homogenizing heterogeneous mixtures of relatively free-flowing and finely divided powdered and granular dry solid materials. The material is blended as the result of repeated splitting and recombining of fractions of the material as the blending chamber is slowly rotated and the material cascades over an array of spaced apart projecting separation elements.

The apparatus of the invention is illustrated in the accompanying drawings in which:

Flg. 1 is a side elevation;

FIG. 2 is an end elevation;

FIG. 3 is a fragmentary section on an enlarged scale taken on the line 33 of FIG. 2 and in the direction of the arrows;

Hg. 4 is a section on a reduced scale on the line 44 of FIG. 1 and in the direction of the arrows;

FIG. 5 is a fragmentary section on an enlarged scale taken on the line 5-5 of FIG. 2 and in the direction of the arrows;

FIG. 6 is a fragmentary section on an enlarged scale taken on the line 66 of FIG. 2 and in the direction of the arrows; and

FIGS. 7 and 8 (sheet 1) are fragmentary sections on an enlarged scale showing alternative forms of separation members.

Referring now to the drawings, the blender apparatus according to the present invention comprises a vertically disposed housing, indicated generally at 10, in the form of a relatively shallow, relatively large diameter cylindrical dish or drum having a peripheral flange 11, and a flat circular cover plate 12 secured to the peripheral flange. Housing 10 and cover plate 12 comprise spaced apart parallel side walls and peripheral wall enclosing a narrow vertically disposed blending chamber 13. A plurality of spoke-like radiating reinforcing channel members 14 and 15 are secured against the outside walls of the housing 10 and cover 12, respectively, to impart additional strength and rigidity thereto. A flanged hub 16 is rigidly secured, as by welding, to the center of the outside wall of housing 10.

I-Iub 16 in turn is rigidly secured to a flange 17 carried by shaft 18 which is joumaled in bearings 19 and 20 supported on the top of a stand 21. Shaft 18 is rotated about its horizontal axis driven from a standard motor 22 and speed reducer 23, both mounted on one side of stand 21, sprocket 24, chain drive 25 and sprocket 26 which is secured to the end of the shaft opposite from the housing. The drive sprockets and chain are preferably enclosed within a suitable safety guard Housing cover plate 12 is provided with a plurality of beveled manual access ports 28, each fitted with a mating beveled door or cover 29 supported from a bracket 30 hinged at 31 to the outside wall of the cover plate. As best seen in FIG. 3, door or cover 29 is rotatably supported by a swivel pad from one end of threaded shaft 32 which extends through a threaded plate 33 carried by bracket 30. A hand wheel 34 permits easy application of force to insure tight engagement of door 29 in port 28. A peripheral O-ring 35 insures a tight seal. A pin 36 extending through holes in the free end of the spaced apart bars of bracket 30 and mating holes of the spaced apart projecting arms of a stop member 37 holds the bracket 30 in place to permit application of force to seal the access ports.

.The upper periphery of the housing is provided with one or more tubular entry ports 40 projecting radially outwardly from the peripheral housing wall. As shown in FIG. 5, each tubular port is provided with an outwardly extending peripheral flange 41 at its free end. Port 40 is closed by means of a cylindrical plug 42, which is preferably hollow and provided with a peripheral channel at its inner end adapted to receive an O- ring 43 to insure a tight fit of the plug in the entry port. Plug 42 is provided with a handle 44 to facilitate insertion and removal of the plug. Plug 42 is also provided with an outer sleeve 45 having an outwardly extending flange 46 so positioned as to mate with flange 41 when the plug is in place in tubular port 40. A spring clamp 47 having an inwardly facing channel engages flanges 41 and 46 to retain plug 42 in place during operation of the blender. The opposing faces of flanges 41 and 46 are desirably provided with an annular channel adapted to receive an O-ring 48 to further insure sealed closure of the entry port.

The bottom of the housing is provided with a downwardly and inwardly tapering discharge hopper 50 having spaced apart parallel side walls and communicating through the peripheral wall with the bottom end of chamber 13. As best seen in FIG. 6, a discharge port 51 extends from the bottom of hopper 50 on one side. Discharge port 51 is in the form of a flanged tube fitted with a flanged plug 52, the overall structure of the tube and plug corresponding generally to that of the entry port and plug described in detail above. The opposite side of hopper 50 is provided at the bottom with a gas inlet port 53 fitted with a plug 54 whose structures likewise correspond generally to those of tne entry port and plug described in detail.

The interior of chamber 13 is provided with a large number of transverse horizontal splitting or separation elements projecting into the chamber from either or both of the inside walls of housing 10 and cover plate 12. As best seen in FIG. 3, the separation members are shown to be in the form of cylindrical pins 56 and 57. As shown there, and in FIG. 4, pins 56 are mounted on the inside wall of cover plate 12, including the inside surfaces of doors 29, and alternating pins 57 are mounted on the inside surface of housing 10. As shown, the pins extend to span substantially the entire width of the chamber 13 but with a small gap between the end of the pin and the opposite wall surface. This serves to strengthen and reinforce the chamber against collapse from internal vacuum or external pressure. Alternatively, all of the pins may project from one wall surface or the other. Instead of being separately attached elements as shown, the housing and/or cover plate may alternatively be formed with integral projecting separation elements, as by casting, hydraulic forming, or the like.

As shown, the projecting separation elements are free-standing, that is, they are supported only by their bases. Likewise, as shown, the longitudinal axes of the separation members are generally parallel to one another.

As shown in FIG. 4, the separation elements are distributed substantially uniformly throughout the chamber widely spaced apart and on substantially parallel horizontal axes. Although shown as cylindrical pins, the separation elements may take a variety of shapes and forms. For example, they may be in the form of angle irons, or semi-circular scoops, or troughs, so disposed as to scoop up and carry material upwardly in their upward path of travel and then dump that material at the top of their path of travel. As seen in FIGS. 7 and 8, the separation members may be in the form of cones 61 or pyramids 62 extending'into the chamber from the opposite side walls at least about half of the width of the chamber, the elements being secured to the opposite side walls. Desirably, the separation elements are distributed uniformly so as to be present in number between about /2 to 10 for each square foot of crosssectional area of the chamber measured by either the area of the inside surface of the housing or the cover plate. In the illustrated unit the chamber is about 6 feet in diameter and about inches wide. There are 68 pins, each 1- /2 inches in diameter and 4- /2 inches long spaced on 7- /2 inch centers, about 2.4 pins per square foot.

Center rod 58, welded or otherwise rigidly secured to the inside wall surface of housing 10, extends through a center hole in cover plate 12 serving to position the same in the assembly of the unit. Desirably a plurality of vibrator pads 59 and vibrators 60 are secured to the outside walls of both housing 10 and cover plate 12 to prevent adherence of material to the inside chamber walls, particularly during discharge. The blender, when provided with proper fittings, is adapted to be operated under vacuum conditions, or within a controlled atmosphere. All exposed surfaces of chamber 13 are desirably formed from or clad with stainless steel and polished for ease of cleaning and to minimize adhering of material. The apparatus is adapted to blend materials such as foodstuffs, for example, cocoa-sugar mixes, and the like, under sanitary conditions, because of the ease of cleaning. It is adapted to blend sensitive materials, such as gunpowder, under gentle conditions with minimum hazard of explosion due to sparking, static electricity, or the like.

In the operation of the apparatus, heterogeneous mixtures of finely divided dry material to be blended are charged to chamber 13 through access ports 28, or through ports 40 by gravity flow or forced air feed. All ports are sealed tightly. If a controlled atmosphere is desired within the chamber during blending, the desired gas is passed into the housing to purge the chamber of air before it is sealed. The chamber may be filled to between about A to /1 of volumetric capacity, desirably about full. The housing is rotated relatively slowly. In the case of the exemplary apparatus shown in which the housing has a diameter of about 6 feet, the housing is rotated at relatively low speeds up to about 30 rpm, but preferably at speeds of about 15 rpm or less. In general, the larger the diameter of the housing, the slower is the rate of rotation. The housing must necessarily be rotated at less than the critical speed at which the material will be held against the outer periphery of the chamber by centrifugal force.

As the housing rotates, the material resting on the bottom surfaces of the chamber is carried upwardly and, as it approaches the top of the path of rotation, the material tumbles down off of the walls cascading downwardly over the projecting separation elements. As a stream of any particular fractionof material strikes the top of any given pin or similar separation element, it is intercepted and split, with part falling on one side and part on the other. This material then intermixes with similar material falling on opposite sides of other separation elements and again is split as it cascades over the next separation element blocking its free downward travel. This occurs hundreds or thousands of times as the material is tumbled, cascades, is split, recombined, split again, and so on. Thorough intimate mixing and blending is accomplished gently, normally within about 2 to 10 minutes of operation. As compared with cone blenders, there is less likelihood of separation of larger and denser particles as the blender is stopped.

The blender is stopped with the discharge hopper at the bottom, as shown. The material is discharged, desirably by aspiration, by removing plug 54 from the gas inlet 53, removing plug 52 from discharge port 51 and making a gas hose connection with the gas inlet. Then, as gas is blown through the bottom of the discharge hopper, the overlying blended material is withdrawn by aspiration out through the discharge port. Vibrators may be used to dislodge material adhering to the chamber wall surfaces and separation elements.

It is apparent that many modifications and variations of this invention as hereinbefore set forth may be made without departing from the spirit and scope thereof. The specific embodiments described are given by way of example only and the invention is limited only by the terms of the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for blending finely divided dry materials, which apparatus comprises:

A. a housing having a pair of substantially parallel spaced apart side walls and a peripheral wall enclosing a vertically extending closed chamber of relatively large diameter and relatively narrow width, and including a discharge hopper extending outwardly from the peripheral wall and in communication with the chamber,

B. means mounting said housing for relatively low speed rotation about a horizontal axis,

C. at least one material entry port to said chamber and at least one discharge port from said chamber, said entry port being a tube extending radially outward from the peripheral wall of the housing and said discharge port being a tube extending outwardly from one wall of said hoppper at the bottom thereof, both of said tubes being closed with tight fitting plugs,

D. a gas inlet port to said discharge hopper, said port being a tube extending outwardly from one wall of said hopper at the bottom thereof on the side opposite from the discharge port, said tube being closed with a tight fitting plug, and

E. a plurality of relatively widely spaced apart projecting material separation members extending into the chamber from at least one of the housing side walls for splitting a stream of cascading material striking the surfaces thereof, said separation members being disposed generally horizontally on substantially parallel axes substantially uniformly within the chamber in number between about to 10 per square foot of vertical cross-sectional area of the chamber. 2. Apparatus according to claim 1 further characterized in that:

A. at least one of said housing side walls is provided with at least one manual access port,

B. said port is provided with a tightly fitting door, and

C. external means are provided for applying force to said door to maintain the same in sealing engagement with said access port.

3. Apparatus for blending finely divided dry materials which apparatus comprises:

A. a housing having a pair of substantially parallel spaced apart side walls and a peripheral wall enclosing a vertically extending closed generally cylindrical blending chamber of relatively large diamater and relatively narrow width, and including a discharge hopper extending outwardly from the peripheral wall and in communication with the chamber,

B. means mounting said housing for relatively low speed rotation about a horizontal axis,

C. at least one material entry port to said chamber and at least one discharge port from said chamber, said discharge port being a tube extending outwardly from one wall of said hopper at the bottom thereof, and closed with a tightly fitting plug,

D. a gas inlet port to said discharge hopper, said gas inlet port being a tube extending outwardly from one wall of said hopper at the bottom thereof on the side opposite from said discharge port, and closed with a tight fitting plug, and

E. a plurality of relatively widely spaced apart freestanding projecting material separation members extending horizontally into the chamber from at least one of the housing side walls for splitting a stream of cascading material striking the longitudinally extending surfaces thereof, the longitudinal axes of said separation members being generally parallel to one another.

4. Apparatus according to claim 3 further characterized in that said separation meii ibers are disposed substantially uniformly within said chamber.

5. Apparatus according to claim 3 further characterized in that said separation members are present in the chamber in number between about A to 10 per square foot of vertical crosssectional area of the chamber.

6. Apparatus according to claim 3 further characterized in that said separation members are cones.

7. Apparatus according to claim 3 further characterized in that said separation members are pyramids.

8. Apparatus according to claim 3 further characterized in that:

A. at least one of said housing side walls is provided with at least one manual access port,

B. said port is provided with a tightly fitting door, and

C. external means are provided for applying force to said door to maintain the same in sealing engagement with said access port.

9. Apparatus according to claim 3 further characterized in that said separation members are cylindrical pins.

10. Apparatus according to claim 9 further characterized in that alternating pins extend from opposite B. said tube is closed with a tightly fitting plug. 

1. Apparatus for blending finely divided dry materials, which apparatus comprises: A. a housing having a pair of substantially parallel spaced apart side walls and a peripheral wall enclosing a vertically extending closed chamber of relatively large diameter and relatively narrow width, and including a discharge hopper extending outwardly from the peripheral wall and in communication with the chamber, B. means mounting said housing for relatively low speed rotation about a horizontal axis, C. at least one material entry port to said chamber and at least one discharge port from said chamber, said entry port being a tube extending radially outward from the peripheral wall of the housing and said discharge port being a tube extending outwardly from one wall of said hoppper at the bottom thereof, both of said tubes being closed with tight fitting plugs, D. a gas inlet port to said discharge hopper, said port being a tube extending outwardly from one wall of said hopper at the bottom thereof on the side opposite from the discharge port, said tube being closed with a tight fitting plug, and E. a plurality of relatively widely spaced apart projecting material separation members extending into the chamber from at least one of the housing side walls for splitting a stream of cascading material striking the surfaces thereof, said separation members being disposed generally horizontally on substantially parallel axes substantially uniformly within the chamber in number between about 1/2 to 10 per square foot of vertical cross-sectional area of the chamber.
 2. Apparatus according to claim 1 further characterized in that: A. at least one of said housing side walls is provided with at least one manual access port, B. said port is provided with a tightly fitting door, and C. external means are provided for applying force to said door to maintain the same in sealing engagement with said access port.
 3. Apparatus for blending finely divided dry materials which apparatus comprises: A. a housing having a pair of substantially parallel spaced apart side walls and a peripheral wall enclosing a vertically extending closed generally cylindrical blending chamber of relatively large diamater and relatively narrow width, and including a discharge hopper extending outwardly from the peripheral wall and in communication with the Chamber, B. means mounting said housing for relatively low speed rotation about a horizontal axis, C. at least one material entry port to said chamber and at least one discharge port from said chamber, said discharge port being a tube extending outwardly from one wall of said hopper at the bottom thereof, and closed with a tightly fitting plug, D. a gas inlet port to said discharge hopper, said gas inlet port being a tube extending outwardly from one wall of said hopper at the bottom thereof on the side opposite from said discharge port, and closed with a tight fitting plug, and E. a plurality of relatively widely spaced apart freestanding projecting material separation members extending horizontally into the chamber from at least one of the housing side walls for splitting a stream of cascading material striking the longitudinally extending surfaces thereof, the longitudinal axes of said separation members being generally parallel to one another.
 4. Apparatus according to claim 3 further characterized in that said separation members are disposed substantially uniformly within said chamber.
 5. Apparatus according to claim 3 further characterized in that said separation members are present in the chamber in number between about 1/2 to 10 per square foot of vertical crosssectional area of the chamber.
 6. Apparatus according to claim 3 further characterized in that said separation members are cones.
 7. Apparatus according to claim 3 further characterized in that said separation members are pyramids.
 8. Apparatus according to claim 3 further characterized in that: A. at least one of said housing side walls is provided with at least one manual access port, B. said port is provided with a tightly fitting door, and C. external means are provided for applying force to said door to maintain the same in sealing engagement with said access port.
 9. Apparatus according to claim 3 further characterized in that said separation members are cylindrical pins.
 10. Apparatus according to claim 9 further characterized in that alternating pins extend from opposite side walls substantially the entire width of the chamber with a small gap between the end of the pin and the opposite wall, whereby the chamber is strengthened and reinforced against collapse from internal vacuum and external pressure.
 11. Apparatus according to claim 3 further characterized in that: A. said entry port is a tube extending radially outward from the peripheral wall of the housing, and B. said tube is closed with a tightly fitting plug. 